33 Special Types of Invasive Breast Carcinoma: Diagnostic Criteria ...

study of 2658 cases of primary invasive breast carcinoma patients, when histologic
grade, lymph node status, and tumor size were considered, histologic grade was the
most important independent factor in predicting survival. Yet, when histologic type
was also considered in the multivariate analysis, it was found to be independently
significant, although comparatively of less importance than histologic grade.
Furthermore, histologic grading is important, because disagreements continue to occur
between pathologists as to the subclassification of breast carcinoma. This happens
because criteria remain controversial (especially in diagnosing medullary carcinoma
and making distinctions between infiltrating lobular and duct carcinomas), and clearly
mixed and/or intermediate patterns of breast carcinoma occur that can be difficult to
classify. Also, some clinicians appear to more easily accept a histologic grade
designation than a vaguely understood and sometimes controversial subtype
designation. Thus, it is wise to give all invasive breast carcinomas a histologic grade,
including the special types like lobular, mucinous, secretory, adenoid cystic,
tubular/cribriform carcinomas, etc. Often, as noted above, these types receive well
differentiated or mBR grade 1 designation, an expected result given their less
aggressive behavior. An exception is medullary carcinoma, for which controversy
continues regarding diagnostic criteria and prognosis. Medullary carcinoma is almost
always mBR grade 3. In contrast to other studies, Elston et al. (5,6,8) were unable to
show an improved outcome for patients with medullary breast carcinoma, even when
strict morphologic criteria were imposed. I believe medullary carcinoma can be over
diagnosed, and it is a diagnosis difficult to reproduce between competent pathologists
(9). The diagnosis of medullary carcinoma has become uncommon in our practice.
Histologic grade (especially when using standardized criteria such as the Bloom-
Richardson criteria [10-16]) helps place any invasive breast carcinoma into its proper
prognostic and therapeutic category, especially when there is controversy or confusion
about the proper subtype designation.
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